1. Field of the Invention
The present invention relates to a rotational position detecting apparatus for generating electric signals associated with the rotation of an internal combustion engine, such as a cylinder discrimination signal, which are used for various control of the engine.
2. Description of the Prior Art
Conventional apparatuses of the above-described kind are provided with two signal rotors both of which are rotated in synchronism with the rotation of an internal combustion engine. One of the signal rotors generates an angle signal at intervals of a given crank angle, while, the other signal rotor generates a reference signal, for example, at the top dead center position of a specified one of engine cylinders, which reference signal is used for the discrimination of the engine cylinders. However, when only one signal rotor is used to generate the reference signal, it is usual that the single signal rotor is provided with only one projection to effect the discrimination of the engine cylinders. The problem with this arrangement is that, at the start of the engine, the timing of generating a reference signal is delayed on the average, thereby deteriorating the starting performance of the engine. While, when using an apparatus provided with both of a signal rotor for generating a reference signal representative of the top dead center position of each engine cylinder, for example, and another signal rotor for generating a cylinder discrimination signal representative of the top dead center position of a specified engine cylinder, it is possible to solve the above-mentioned problem, but, on the other hand, there arouses another problem of increasing the number of signal rotors, thereby rendering the construction complicated and making it difficult to reduce the size of the apparatus.